This invention relates to a method of forming a support structure on a base, and to an article for use in forming such a support structure.
It is well known to form support structures such as roadways, canal or river or bank linings, mine packs, sea walls, or the like from a material having a honeycomb structure, i.e having a plurality of compartments or cells divided by dividing walls, each compartment or cell being filled with a suitable filler material. Examples of such materials for use in the support structures are Hyson-Cells from M and S Technical Consultants and Services (Pty) Limited, Geoweb from Presto Products Co, Tenweb from Tenax Corp, Armater from Crow Company, Terracell from Webtec Inc, Envirogrid from Akzo Nobel Geosynthetics Co and Geocells from Kaytech.
In making such a support structure using these materials it is generally been the practice for the material with the honeycomb structure to be located on a base, and thereafter for the compartments or cells of the honeycomb structure to be filled with a suitable filler material. However, it has been found that in certain circumstances when the compartments are being filled with the filler material, the walls of the compartments, being flexible, buckle or collapse, which then causes various additional problems such as the creation of a layer of filler material on top of the cells, sometimes a layer of filler material underneath the cells. and gaps or cracks between adjacent blocks, all of which lead to a support structure which is not suitable to perform the required function. These problems are illustrated schematically in FIG. 4 of the accompanying drawings.
There is thus a need for a method of overcoming this problem.
According to a first aspect of the invention there is provided a method of forming a support structure on a base from a framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube, the compartments being arranged in rows and columns so that the tube divided by dividing walls has a honeycomb structure, which method comprises the steps of:
(1) locating a flexible string or a rigid stay through a line of compartments at or near each edge of the framework. and optionally locating flexible strings or rigid stays through one or more lines of compartments intermediate the edge lines of compartments;
(2) attaching the ends of the strings or stays to fixed objects to support the framework with a first end of the tube on the base and a second end of the tube above the first end; and
(3) filling some or all of the compartments with a filler material so that at least some of the compartments are adjacent one or more other compartments filled with the filler material to support and be supported by the adjacent compartments.
In other words, assuming that the framework is substantially rectangular in plan view, a string or a stay is located at least in a line of compartments at or near each of the four edges of the framework.
The flexible string or rigid stay may be located in position in a line of compartments by making a series of holes in the walls of the compartments in the line, and then passing the flexible string or rigid stay through the holes.
The use of flexible strings or rigid stays assists in holding the framework in position before the filler material is filled into the compartments. By strings is meant any flexible rigging. flexible lacing or similar flexible wire material. By stays is meant any rigid rigging, including rigid wire. rods or pipes, or the like.
Preferably, two flexible strings or rigid stays are located through a line of compartments., one string or stay near the top of the tube and the other string or stay near the bottom of the tube.
Preferably, at any point where a string or a stay intersects with another string or stay in a particular compartment, there is provided a support in the compartment to support the intersecting strings or stays.
Alternatively, the support may be used to support the strings or stays at a location other than at intersections.
The support is preferably a rigid support and may comprise, for example, a hollow cylinder with slots, or a solid rod with grooves cut therein, or a stand with hooks thereon to receive and support the strings or stays.
The framework, i.e the tube and the dividing walls, may be made from any suitable flexible material. Although the material must possess some degree of flexibility, the degree of flexibility may range from very flexible up to semi-rigid. The flexible material may be for example a plastics material such as for example a co-extruded or a bi axially extruded plastics material; a plastics laminate material such as for example a laminate of a plastics material and a metallic material or a textile material; a metallic material; a woven or non-woven textile material; a paper or cardboard material. and the like.
The flexible material is preferably a suitable plastics material.
The framework may have any suitable height and any suitable compartment size. For example. the height of the framework may range from 2 mm to 10 m inclusive, and each compartment may have a wall length of from 5 mm up to 2 m.
The compartments in the framework may have any suitable cross-section. such as square, hexagonal or octagonal, but preferably have a square cross-section, i.e each compartment is defined by four walls of substantially equal lengths.
The filler material may be any suitable filler material such as for example an inert filler material, e.g sand or gravel or the like, or a composition comprising a filler material and a settable binder therefor. Examples of such compositions include:
(i) an inert filler material such as sand or gravel or the like, and a cementitious binder, for example ordinary Portland Cement;
(ii) an inert filler material such as sand or gravel or the like and a bituminous binder;
(iii) a filler material such as soil treated with a suitable chemical composition such as calcium chloride, a lignin sulphonate or an ionic liquid to cause the soil to bind or set;
(iv) a filler material such as sand or gravel or the like and a resin binder, for example (a) a thermosetting resin such as polyurethanes and polyesters, (b) a thermoplastic resin such as polyethylene, EVA, or PVC, and (c) a suitable wax.
The settable composition may include a conventional foam or foaming agent so that the final set composition is a foamed composition, to reduce the weight thereof.
The support structure may be made from a single framework as described above, or the support structure may be made from a plurality of frameworks laid side-by-side on the base, each framework being as described above and being supported as described above and being filled with the filler material as described above In this case, the compartments along an edge of a first framework will abut the compartments along an adjacent edge of an adjacent framework.
According to a second aspect of the invention there is provided a combination of a framework comprising a tube of a flexible material divided by dividing walls of a flexible material into an array of compartments or cells running the length of the tube. the compartments being arranged in rows and columns so that the tube divided by diving walls has a honeycomb structure, and a plurality of flexible strings or rigid stays each located in a line of compartments, the combination including a flexible string or rigid stay at or near each edge of the framework, for use in forming a support structure by the method described above.
The flexible strings or rigid stays are typically attached to fixed structures or are themselves supported on rigid auxiliary support members, such as soil nails or anchoring pegs or the like.
Each flexible string or rigid stay tray be provided with holding means, to hold the string or stay in position in the framework, i.e to prevent the string or stay from being pulled out of the row or column of compartments in which it is located.
For example, a flexible string may be knotted within a compartment or outside an edge compartment, to prevent the string from being pulled out of the relevant compartment. Alternatively a suitable holding means such as a plate with a hole therethrough or a mesh, may be located in a compartment, with the flexible string or rigid stay passing through the hole in the plate or a hole in the mesh and being ripped thereby.